Grammar-Quizzes.com gave the following rules that will help us learn the Plural Form–all (Dogs are) and The–classification (The Dog is).

A. Plural Form–all (Dogs are)
– In this example, plural form expresses all in general. This is a usage commonly found in everyday speech, books, articles, and magazines. If the plural and singular noun form is the same (e.g., fish, deer, and elk) or the noun is non count (e.g., water, air, love) then use the singular form.
Examples:
- Wolves hunt in packs.
- Deer feed primarily on leaves.
– Using no article before a plural form noun refers to all (even if some do not fit the generalization.) This form is used when speaking in general about the qualities and characteristics of the noun.
Example:
Dogs with heavy coats and strong legs can pull sleds over snow and ice.
B. The–classification (The Dog is)
– The before the singular noun form (“the wolf”) expresses all in the class (type, or kind). This is a usage particular to text found in science books, encyclopedias and scholarly publications for discussing the quality, character of behavior of an entire classification.
Examples:
- The wolf (Canis Lupus) hunts in a pack.
- The deer is a ruminant mammal.
– Using the before a plural noun (a group) or non count noun (collective, mass, concept) refers to something known—by previous mention, shared knowledge, an expected part, uniqueness, etc.
Example:
The dogs are named Darryl and Hannah.
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